1. Field of the Invention
This invention relates to the field of cutting tools for plastic pipes and more particularly to the field of manually operated cutting tools with handles that are spring biased apart to open the jaws of the tool.
2. Discussion of the Background
Cutting tools for plastic pipes are widely used throughout the world and are an essential piece of equipment for virtually anyone who works with plastic pipes. In the typical design, two elongated members are pivotally connected together in a scissors-like manner. In one popular arrangement such as in applicants"" U.S. Pat. No. 4,336,652 and D266,736, the handles of the tool are manually manipulated to separate them and open the jaws of the tool to receive the plastic pipe to be cut. In doing so, the handles can be rubbed along the user""s leg to separate them and open the tool""s jaws or the user can extend his or her fingers to separate the handles. Once opened with the pipe received between the jaws of the tool, the handles can then be squeezed together to drive the edge of the knife blade on one of the jaws into the pipe. At the same time, the tool is normally swung relative to the pipe. In doing so, the knife edge continues to be driven into the pipe until the pipe is eventually severed.
Such cutting tools can be provided with a spring or springs to bias the handles apart and the jaws into an open position to receive the pipe. When a number of cuts are to be done, many users find it more efficient to have a spring-biased tool rather than one whose handles must be manually opened for each cut. Adding a spring, however, increases the complexity and cost to manufacture and assemble the tool. As for example in U.S. Pat. No. 191,416 to Fetter, U.S. Pat. No. 217,583 to Cannon, U.S. Pat. No. 392,717 to Carson, U.S. Pat. No. 929,749 to Bishop, U.S. Pat. No. 1,261,284 to Phelps, U.S. Pat. No. 1,757,173 to Dingman, U.S. Pat. No. 1,802,903 to Bryant, U.S. Pat. No. 2,006,133 to Fowler, U.S. Pat. No. 3,257,723 to Cercone, and U.S. Pat. No. 4,073,059 to Wallace, rivets or screws are necessary to secure the spring to one of the handles. In other patents, the spring must be welded to the tool as in U.S. Pat. No. 1,702,801 to Smith and U.S. Pat. No. 5,058,277 to Kishimoto or special posts must be designed into the tool itself to secure the spring in place as in U.S. Pat. No. 352,560 to Neff, U.S. Pat. No. 3,562,908 to Rogers, U.S. Pat. No. 5,203,084 to Kuo, U.S. Pat. No. 5,860,568 to Mallalieu, and U.S. Pat. No. 5,946,752 to Parrish. Still others require that even more elaborate structure be designed into the tool as in U.S. Pat. No. 4,400,876 to Brown and U.S. Pat. No. 4,633,587 to Harrison or special structure be added to both handles to support the spring as in U.S. Pat. No. 5,930,900 to Chang and British Patent No. 1,196,023 to Rogers. In many cases, such additional complexity and cost to the manufacture and assembly of the tool prices it out of the market.
In contrast, the spring-biased cutting tool of the present invention uses a simple and inexpensive leaf spring with a curved lip on one end that easily clips over a conveniently positioned edge on the tool. In this manner, the spring-biased tool of the present invention can be manufactured and assembled at a cost that is very competitive in the market.
This invention involves a spring-biased cutting tool for plastic pipes. The tool includes two elongated members pivotally connected to each other in a scissors-like manner. Each elongated member has a handle portion and a jaw portion with one jaw portion including a knife blade and the other an anvil. To assemble the elongated members, one of them is provided with a central aperture or hole through which the other member can be passed to form the scissors-like shape.
In the preferred embodiments, the aperture in the one elongated member is defined by a plurality of edges wherein one edge portion is designed to support an end of a leaf spring. The leaf spring then extends across to abut against the other elongated member of the tool and bias the handles of the tool apart to open the jaws. The attached end of the leaf spring has a curve in it forming a lip. To assemble the spring on the one elongated member, the curved lip is flexed open and pinches the edge portion of the aperture between it and a section of the leaf spring immediately adjacent the lip. In this manner, the leaf spring can be easily and quickly clipped over the edge portion of the aperture on the one elongated member of the tool. The aperture edge portion is preferably pinched between the extreme end or edge of the curved lip and a section of the leaf spring immediately adjacent the lip. The force of the pinch including the physical, frictional engagement of the lip with the aperture edge portion securely keeps the leaf spring in place. In a preferred embodiment, a retaining protuberance or step is added to the structure of the edge portion of the aperture to further ensure that the leaf spring cannot be easily disengage from the tool.